MASSIVELY PARALLEL ITERATIVE DETERMINATION OF STRATIFIED DIELECTRIC PARAMETERS FROM SCATTERED-FIELD MEASUREMENTS

The remote determination of dielectric constants of stratified dielect rics, through solution of the inverse-scattering problem, has practica l application in many fields. We use a simple one-dimensional model to determine the salient characteristics of stratified layers of dielect rics given a finite number of reflection coefficients for various freq uencies in the microwave X-band region. One of the key concepts of thi s research is the optimization that is necessary to find a global mini mum of the highly nonlinear function that specifies the scattering coe fficients. This was achieved by use of a simple iterative method where by 16,384 iterative procedures that employ random starts are run simul taneously on a MasPar, which is a 16,000 processor single-instruction/ multiple-data computer. Results show that one can solve for the refrac tive index or thickness of a number of dielectric layers with thicknes ses of the order of one third of a wavelength or less by using this ty pe of nonlinear optimization.